In recent years, hard copying technology has made rapid progress with the performance improvement of computers and their spread. As the recording method of hard copying, there have been known, for example, dye diffusion thermal transfer recording, electrophotographic recording, and ink jet recording.
The ink jet printers take a recording method in which ink drops are discharged as a high-speed ink jet from the nozzle of the printer toward the recording paper to be printed. The ink jet printers have been rapidly spread as the terminal units of computers for office, home, or personal use because of their high applicability to full color printing, their easy down sizing, and their low noise in the printing. Furthermore, the ink jet printers have been expected to find applications in various fields of industry, such as large-sized signboards, because of their improvement in printing quality close to silver salt photography and their high applicability to large-scale printing.
The printing by the ink jet recording method is greatly influenced by the properties of ink and recording materials, and the compatibility between the ink and the recording materials, in addition to the performance of hardware.
The ink to be used in the ink jet recording contains a recording agent for image formation and a liquid medium (mainly water) for the dispersion or dissolution of the recording agent as the essential ingredients, and further contains various additives, if necessary, such as dispersing agents, surfactants, viscosity modifiers, resistivity modifiers, pH modifiers, antifungal agents, and stabilizers for the dissolution or dispersion of the recording agent. As the recording agent, there have been used direct dyes, reactive dyes, acidic dyes, basic dyes, food dyes, disperse dyes, or various pigments. For this reason, the properties of ink may vary with the ink-manufacturing makers and the kinds of ink.
Various recording materials to be used in the ink jet recording have been proposed, for example, a recording material with an ink-receiving layer containing an inorganic pigment and a water-soluble resin, and a recording material with an ink-receiving layer composed mainly of a water-soluble resin. In addition, various additives have been proposed for the improvement in the speed of ink absorption into the ink-receiving layer and for the enhancement of water resistance and moisture resistance.
These recording materials are not suitable for the recent high-speed printing and they require the use of specific ink for better printing. This is because many ink products available from different makers have different characteristics.
To increase the speed of ink absorption, a polymer with a polar group, either cationic or anionic, should be incorporated in the ink-receiving layer. Even if an ionic property is given to the ink-receiving layer, the resulting recording material is only suitable for the use of specific ink; in particular, it cannot attain rapid absorption of other ink products with different values of pH.